package demo9;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sr=new Scanner(System.in);
        Integer n=sr.nextInt();
        if(n>=0&&n<=9){
            System.out.println(n);
        }else if(n>=10&&n<=15){
            switch (n){
                case 10:
                    System.out.println("A");break;
                case 11:
                    System.out.println("B");break;
                case 12:
                    System.out.println("C");break;
                case 13:
                    System.out.println("D");break;
                case 14:
                    System.out.println("E");break;
                case 15:
                    System.out.println("F");break;
            }
        }else {
            System.out.println("Invalid input");
        }
    }
}
